In 1859, the Democratic Party in the state was divided over slavery, specifically the potential expansion of slavery into Kansas. Two factions emerged for the 1859 state general election: the Lecompton faction, which supported the proposed pro-slavery constitution in Kansas, and the abolitionist Anti-Lecompton faction.
Candidates' party affiliations obtained from the 9/10/1859 Sacramento Daily Union. https://cdnc.ucr.edu/?a=d&d=SDU18590910.2.2&e=-------en--20--1--txt-txIN--------
Source for Popular Vote data: California State Archives, "For State Treasurer," Statement of the votes polled at a general election held in the State of California on the seventh day of September A.D. 1859 (Sacramento, 1859)